Pellet impact bore hole enlarger



May 17, 1955 A. B. HILDEBRANDT PELLET IMPACT BoRE HOLE ENLARGER FiledMay 15, 1955 Qlexnnder ED. Hildebrandt ave r1 t or 615D). CbbownezPELLET IMPACT @GRE HLE ENLARGER Alexander B. Hildebrandt, Tulsa, Okla.,assigner to Esso Research and Engineering Company, a corporation ofDelaware Application May 13, 1953, Serial No. 354,805

7 Claims. (Cl. Z55- 61) The present invention relates to a method andapparatus for enlarging the lower end of a bore hole. More particularly,the invention concerns apparatus for utilizing the pellet impactprinciple for increasing the diameter at the bottom of a bore hole.

It is often desirable to increase the productivity of an oil well byenlarging or under-teaming the bore hole in the region of the producingformation so as to increase the area from which production takes place.Conventionally such under-reaming is done by drilling apparatus of arather complicated nature. The present invention enables suchenlargement to be elfected with relatively simple apparatus.

The basic principles of the pellet impact technique for the drilling ofbore holes involve the use of a stream of uid pumped from the surface ofthe earth through a 5 tubular member to a jet nozzle assembly adjacentthe bottom of the bore hole. The jet nozzle assembly is adapted todirect a high velocity jet of fluid against the formation being drilledand is provided with means for entraining in the jetted iluid amultitude of pellets which are accelerated to high velocity in the jetstream and thereby acquire considerable kinetic energy so that when thepellets impinge against the formation the resulting percussive andfracturing forces exert a drilling action. Preferably the pellets thatare employed are smooth, nonabrasive and essentially spherical and areof substantial size, preferably in the size range of about l/s to aboutl in diameter. lt is preferred that hard, tough metallic alloys beemployed as the pellet material. The basic principles of the techniqueof drilling by pellet impact are set forth in copending application Ser.No. 268,873, iiled by Philip S. Williams, on January 29, 1952, andentitled Pellet Impact Drilling Method and Apparatus.

The present invention is directed to the use of the pellet impacttechnique for the enlargement of a bore hole adjacent the bottomthereof. A fluid jet issuing from a primary nozzle is directed into asecondary nozzle wherein pellets are entrained in the iluid jet and thejetted lluid and pellets are discharged from the lower end of thesecondary nozzle which is angled or bent in such a manner that thepellets impinge on the side of the bore hole and thereby enlarge thesame. A tail pipe on the nozzle assembly creates a narrow annulus in thebore hole through which the returning uid and pellets are directed toenter the tail pipe for recycling upwardly to the entrance of thesecondary nozzle. A slotted deflector adjacent the entrance to thesecondary nozzle directs the pellets to the primary jet entering thesecondary nozzle while permitting returning fluid to pass upwardly inthe bore hole annulus.

A fuller understanding of the nature of this invention may be obtainedby reference to the accompanying drawing in which:

Fig. 1 is an elevational view in section illustrating the upper portionof one form of apparatus suitable for the practice of this invention, inposition in a bore hole, showing the primary nozzle, means for directingpellets into the lCC jet entering the secondary nozzle and means fordirecting the returning stream of fluid up through the bore holeannulus, and

Figure 1A is a lower continuation of Figure 1 and illustrates the mannerin which the pellets leaving the secondary nozzle are directed outwardto effect a desired bore hole enlargement and the manner in which thepellets fall to the bottom of the bore hole to be recycled for entryinto the secondary nozzle.

Referring now to particular details of the apparatus as depicted inFigures 1 and 1A, the drilling apparatus is supported in the bore hole 1by means of a tubular support 2 which may be a conventional drillstring. Attached to the lower end of the drill string or support 2 is anelongated tubular member 3 having a lower portion of smaller internaldiameter 9. Arranged within the upper portion of tubular member 3 is aprimary nozzle 4. Positioned below primary nozzle 4 is an open secondarynozzle 14 the lower portion of which, designated as l5, curves outwardlyand terminates exterior of tubular member 3.

The lower end of tubular member section 9 flares outwardly to provide ashoulder portion 10. A sleeve l2 lits siidably about the shoulderportion 10 and has an upper portion 13 of restricted diameter so as toslidably engage section 9 of the tubular member 3. Thus sleeve 12 canslide vertically on portion 9 but is limited in its downward travel byengagement of the restricted portion 13 with the shoulder 10.

A packer member S supported on sleeve 19 surrounds tubular member 3. Itis not necessary that packer member S furnish a fluid tight seal in thebore hole annulus but merely that it be of suicient size so as toessentially prevent fluid ow past the packer in the bore hole annulus.Thus a packer size may be selected that is approximately that of thebore hole diameter and no provision is necessary for expanding thepacker against the bore hole wall to provide an absolute seal.Preferably sleeve 19 is fixed against vertical travel along tubularmember 3 but is adapted to rotate freely with respect to member 3 sothat packer member 8 will oler no resistance to rotation of member 3 andthus also preventing undue Wear on the packer member. This can beaccomplished for example by means of annular rings 2l) tted intoappropriate grooves in member 3. Packer member 8 is preferablyconstructed of somewhat resilient material.

Fitted within tubular member 3 adjacent the lower termination of primarynozzle 4 is a perforated or slotted baille or guide member 1S that isadapted to permit fluid to pass through it into the chamber 11 that isdefined by nozzle 4 and the interior of tubular member 3. The slots inmember 18 are of such size that the pellets employed in the drillingoperation will not pass therethrough. Thus these pellets will bedirected into the top of secondary nozzle 14. Fluid that enters chamber11 will pass out into the bore hole annulus above packer 8 through slots7, fluid communication between chamber 11 and the interior of the drillpipe being blocked olf by the enlarged throat 6 of the primary nozzle.It is preferred that guide member or dellector 18 be curved in themanner shown to aid in directing pellets into the nozzle 14.

To conduct the desired bore hole enlarging operation a plurality ofpellets are placed at the bottom of the bore hole and then the apparatusdescribed is lowered into the bore hole. Fluid is then pumped down thedrill pipe through nozzle 4. As it leaves this nozzle the fluid isconverted into a high velocity jet stream which then enters secondarynozzle lil from whence it is directed laterally against the wall of thebore hole. Packing member 8 prevents the ejected fluid from passingdirectly up the borehole annulus so that instead the fluid must flowdown through the annulus between sleeve l2 and the bore hole and then upthrough the tail pipe comprising sleeve 12 and extension member 9. Thevelocity of the stream flowing upward through the tail pipe will besuciently great to carry pellets with it up to the baille member 18which by its construction will direct the pellets into the entrance ofthe secondary nozzle 14. Entry of the pellets into the secondary nozzleis also facilitated by the aspirating effect created by passage of theuid jet from the primary nozzle into the secondary nozzle. A portion ofthe upowing stream of lluid will also enter the secondary nozzle and thebalance will pass up through passageway 11 and out through ports 7 intothe bore hole annulus to constitute the returning stream of uid owing upup the bore hole. rl`he pellets that enter the secondary nozzle 14 willbe admixed with the high velocity jet of tluid and will attainsubstantially the same velocity as the tluid stream so that they will bedirected with great force laterally against the bore hole wall to drillan enlarged portion designated as 16. It will be observed that thesecondary nozzle has a somewhat greater diameter than the primary nozzlein order to accommodate the jet of fluid in combination with the volumeoccupied by the entrained pellets.

lt can be seen by virtue of the arrangement of sliding sleeve 12 thatsome vertical adjustment of the position of nozzle 14 is possible whilethe bottom of sleeve 12 at all times rests on the bottom of the borehole, thus enabling the drilling of an enlarged hole similar to theshape illustrated. By rotating the drill pipe the jetted stream ofpellets can be directed in every direction about the bore hole.

The bottom of sleeve 12 is provided with slots 17 so as to allow sleeve12 to rest on the bottom of the bore hole and at the same time provideaccess of returning fluid and pellets to the interior of sleeve 12.

It is obvious that the drilling apparatus of this invention could beused for enlarging a portion of a bore hole some distance from thebottom by providing a suitable plug in the bore hole adjacent the areato be enlarged, the plug then serving in lieu of the bore hole bottom asa support for sleeve 12.

The scope of this invention is to be limited only by the followingclaims.

What is claimed is:

l. A drilling apparatus for enlarging the bottom of a boreholecomprising an elongated tubular member adapted for placement in the borehole, a nozzle assembly supported by the tubular member and including anozzle element adapted to direct a high velocity stream of fluid andentrained pellets laterally against the wall of the bore hole, meanseiecting recycling of pellets from the bottom t of the bore hole intosaid nozzle assembly, packing means essentially blocking fluid ow in theborehole annulus between a region above said nozzle element and theregion adjacent said nozzle element, and conduit means for conducting aportion of the return stream of fluid from a region adjacent the entryof recycled pellets into said nozzle assembly to a region in the borehole annulus above said packing means.

2. Apparatus as defined by claim l including a perforated baflle memberat the lower end of said conduit means adapted to permit uid flowtherein while prevent ing the entry of pellets therein.

3. A drilling apparatus for enlarging the bottom of a bore hole in theearth comprising an elongated tubular member adapted to be placed in aborehole, a first downwardly directed nozzle member supported by saidtubular member and having its upper opening in fluid communication withsaid tubular member, a second nozzle element supported by said tubularmember below said rst nozzle element with its upper opening generallyaligned with and spaced a fixed distance from the outlet of said tirstnozzle element, the lower end of said second nozzle element beingdirected outwardly in a lateral direction, a second tubular memberextending below said second nozzle and terminating at its upper endadjacent and in lluid communication with the upper opening of saidsecond nozzle element, a fluid conduit member arranged in generalparallel relation to said primary nozzle with its lower end in uidcommunciation with said second tubular member and its upper end in fluidcommunication with the borehole annulus, a perforated baflle separatingsaid second tubular member and said conduit member and a packing elementsurrounding said first nozzle element and said conduit member toessentially prevent duid tlow past said packing element in the bore holeannulus adjacent thereto. f

4. Drilling apparatus as defined by claim 3 including a sleeve memberarranged in telescopic sliding relation with said second tubular memberand extending downwardly therefrom whereby to provide a pellet returnchannel of variable length.

5. A drilling apparatus for enlarging the bottom of a borehole in theearth comprising an enlarged tubular member adapted to be placed in abore hole, a rst downwardly directed jet nozzle element positionedwithin said tubular member with its upper end in open communication withthe bore of said tubular member, means blocking tluid communicationbetween said bore above said nozzle element and the chamber defined bysaid nozzle element and said tubular member, a perforated battle memberclosing the lower end of said chamber, a second nozzle elementpositioned within said tubular member with its upper open end in generalalignment with said rst nozzle element and spaced therefrom a suicientdistance to provide an entrance for pellets of appreciable size, thelower end of said second nozzle element being directed outwardly in alateraldirection and terminating exterior of said tubular member in aregion above the lower termination of said tubular member, and anannular packing member supported on said tubular member in a regionintermediate the ends of said chamber, said packing member being of sizeto essentially prevent lluid fiow past said packing element in theborehole annulus adjacent thereto, and said tubular element having atleast one port in its outer wall com# municating with said chamber at apoint above said packing element.

6. Apparatus as defined by claim 5 wherein said packing element isrotatably mounted on said tubular member.

7. Apparatus as defined by claim 5 including a sleeve member arranged intelescopic sliding relation with said tubular member and dependingtherefrom whereby to provide a pellet return channel of variable length.

References Cited inthe tile of this patent UNITED STATES PATENTS1,547,461 Steele July 28, 1925 2,018,285 Schweitzer et al. Oct. 22, 19352,072,627 Zublin Mar. 2, 1937 2,233,260 Hawthorne Feb. 25, 1941

